State of Hawaii

MONTH: December 2007

PREPARED: January 9, 2008

State: [Text data table for rain gages]

December weather can be summarized as “wet and windy” across the State of Hawaii and the wettest month since March 2006. The main weather event was a strong low pressure system and associated cold front that swept in from the northwest on December 4 bringing damaging winds and flash flooding as it progressed eastward across the island chain. Forward progress of the cold front slowed near Maui which marked an easing of the winds a bit but prolonged the heavy rains. The low pressure system evolved into a kona low on December 6 north of Kauai and kept very moist south to southwest winds over the islands with brief but frequent moderate to heavy showers. On December 8, the system finally weakened and rapidly moved northeastward allowing more stable conditions to become established. Kauai had event rain totals mostly in the 4- to 8-inch range with flooding problems forcing closures of the usual vulnerable roads such as Kuhio Highway at the Hanalei Bridge. Oahu took the brunt of the wind damages but rain totals were limited to the 3- to 6-inch range and no significant problems. In contrast, Maui County and the Big Island saw the heaviest rains with several sites recording event totals in the 10- to 15-inch range and isolated spots recording higher amounts. On Maui, locations along Waiohuli Gulch, which includes portions of Keokea and Kihei, experienced substantial flood damages as a result of significant debris-laden flows. Estimates of property and infrastructure damage will likely run into the millions of dollars. Considering the scale of flooding, it was fortunate there were no flood-related deaths and only one significant injury. Maui County personnel rescued two individuals from the roof of their home after it was swept downhill over 100 yards. On the Big Island, flash flooding forced the closure of several roads in Kailua-Kona, Honaunau, and the Kawa Flats area of Kau near Punaluu.

Moderate trade winds resumed on December 11 but quickly became strong from December 13 through 16 with abundant shower activity. Trade wind strength dropped slightly on December 17 and remained at fresh to strong levels for most of the remainder of 2007. An upper level trough over the Hawaiian Islands along with a shear line in the lower levels brought rainy conditions to the state on December 30 and 31. Windward areas of Oahu received 3 to 5 inches of rain and flash flooding in Waikane Stream briefly forced the closure of Kamehameha Highway. Heavy rains over Molokai also resulted in small stream flooding along Kamehameha V Highway on the morning of New Year’s Eve.

The wet conditions for the second consecutive month helped ease drought problems which established itself in May 2007. Mandatory water use restrictions in Upcountry Maui and Waimanalo have been removed due to improved reservoir supplies. For several months, farmers on irrigation water in the Waimanalo area were forced to cut back use by 30 percent.

Island of Kauai : [December 2007 map] [Year-to-date map]

All of the gages on Kauai recorded near to above normal rainfall during December. As usual, the U.S. Geological Survey’s (USGS) gage on Mount Waialeale recorded the highest total on the island (44.96 inches, 99 percent of normal). However, the Kokee gage posted the most noteworthy statistics including the highest daily total of 5.28 inches on December 7, a 2-day total of 9.90 inches on December 6 and 7, and the third highest monthly total since archiving gage data in January 1991. Measurable rainfall (at least 0.01 inches) occurred daily at Kokee, Wailua, and Lihue Variety Station and 30 out of 31 days at Kapahi.

Despite the wet conditions in December, most of the available gage totals for 2007 remained in the below normal range. Mount Waialeale ended 2007 with 336.13 inches (79 percent of normal), the highest annual total statewide but well off its normal amount of nearly 424 inches.

Island of Oahu: [December 2007 map] [Year-to-date map]

Most locations across Oahu recorded near to above normal rainfall totals for December. Once again, the highest total, 24.47 inches (127 percent of normal), came from the U.S. Fish and Wildlife Service’s gage at the Oahu Forest National Wildlife Refuge (NWR). Usually, the Oahu Forest NWR monthly total is among the top 3 statewide but heavy rains on the other islands pushed this site’s total out of the top 10. Punaluu Pump recorded the highest daily total of 3.93 inches during the shear line passage on December 30. The shear line also produced intense rainfall at several locations, including 15-minute totals of 0.81 inches and 0.75 inches at Olomana Fire Station and Hakipuu Mauka, respectively. In terms of frequency, measurable rain occurred daily at Luluku, Wilson Tunnel, and Nuuanu. A NOAA forecaster in Palolo Valley also recorded measurable rain every day though interestingly the Manoa Lyon gage did not, having logged rainfall on “only” 30 out of 31 days.

Wet conditions for the second consecutive month helped push 2007 totals into the near normal range at many locations on Oahu. The Oahu Forest NWR gage closed out the year ranked third statewide with 186.53 inches (91 percent of normal). Waianae Boat Harbor finished with the lowest total and percent of normal value with 10.21 inches and 49 percent, respectively.

Maui County: [Maui December 2007 map] [Year-to-date map] [Molokai/Lanai December 2007 map] [Year-to-date map]

As if trying to make up for missed rainfall earlier in the year, Maui County experienced the wettest conditions statewide during December with most sites posting well above normal totals. The USGS gage at Puu Kukui recorded 60.22 inches (166 percent of normal) which was the highest total statewide. Even Kaupo Gap’s 41.10 inches on the southeast slopes of Haleakala nearly surpassed Mount Waialeale’s total of 44.96 inches. The highest recorded daily total occurred at Puu Kukui with 6.00 inches on December 5, though radar estimates from the same day indicated spots with more than 10 inches above the Keokea area in Upcountry Maui. Gages at Lanai City (17.12 inches) and Mahinahina (20.12 inches) both posted the highest monthly totals recorded based on data archived since January 1991. The Kaunakakai Mauka gage (10.00 inches) posted its second highest monthly total on record, beaten only by 16.45 inches in January 2004.

A second consecutive month of wet conditions pushed 2007 totals into the near to above normal range at most locations in Maui County. Puu Kukui had the highest county-wide total of 234.65 inches but also had the lowest percent of normal value at 61 percent. The Puu Kukui 2007 total was also the second highest in the state below only Mount Waialeale’s 336.13 inches.

Island of Hawaii: [December 2007 map] [Year-to-date map]

All rain gages on the Big Island recorded near to well above normal totals for the month of December. The gage at Glenwood posted the highest monthly total of 38.22 inches (222 percent of normal) and 7 other gages had totals greater than 20 inches. A notable total is Pali 2’s 25.32 inches, an incredible 517 percent of normal. Moreover, 22.08 inches of the total occurred during only a 7-day period from December 2 to 7! Pali 2 is located in the Kau Desert and is normally a dry area under prevailing trade wind conditions. However, several days of moist southerly flow in early December helped make this site look more like a wet “windward” locale than a desert site. The highest daily total was 8.62 inches recorded at Kapapala Ranch on December 5 associated with the early December cold front/kona low.

Wet conditions in December helped raise 2007 totals into the near to above normal range at several sites on the Big Island. Glenwood’s 176.30 inches (107 percent of normal) topped all other Big Island totals for the year and finished fourth highest in the state. Most sites in the Hamakua and Kohala sections of the island ended up with below normal totals. Pali 2’s 54.37 inches from the Kau Desert surpassed totals from Honokaa and all 6 Kohala area gages.

Data Sources: Data used in this report are largely from National Weather Service sources including climate network weather observation stations at Lïhue, Honolulu, Kahului, and Hilo, the Hydronet state network of automated rain gages, and selected Cooperative Observer sites. Additional data come from automated rain gages operated by the State of Hawai‘i Department of Land and Natural Resources, the US Geological Survey, the US Bureau of Land Management, the US National Park Service, the Department of Defense, and the US Fish and Wildlife Service. Data presented here are not certified and should be used for information purposes only.

Kevin R. Kodama
Senior Service Hydrologist
NOAA/NWS Weather Forecast Office Honolulu